Description: Preliminary data from the applicant's lab suggests that tryptopha is required for the proliferation, but not the activation of T cells. The enzyme, indoleamine 2,3-dioxygenase (IDO), is produced by some macrophages, an results in anergy of T cell which see antigen presented by these macrophages. Using tryptophan deficient medium and anti CD3/CD28 activation, they will examine the biology of the T cell arrest. Initially they will determine the cell cycle arrest point induced by tryptophan starvation. They will examine RN for cell cycle control genes (CDK1, CDK4, cyclin E, p21 p27) apotosis genes (fas, bcl2, bax, bak, bclx,) cytokines IL2, IFN-g, IL2R), they will also examine the same proteins by western blot as well. Cell surface phenotyping will be performed. They will determine if CTL activity can be developed under tryp- culture. Again CD3/CD28 activation will be carried out and induction of perforin, granzyme and TNF will be assessed. Finally they will test if already activated CTL can kill macrophage targets. They will determine if energy induced is reversible, and finally determine in HIV infected macrophages have IDO induced, and if anergized T cell are present in HIV+ asymptomatic individuals.